1. Field of the Invention
The present invention relates to an image pickup lens for a solid-state image pickup element which is used in a small-sized imaging device for a small-sized, thin electronic device.
Specifically, the present invention relates to an image pickup lens for a solid-state image pickup element which is used in a small-sized imaging device for small-sized, thin electronic devices such as a portable terminal, a PDA (Personal Digital Assistant) and the like.
2. Description of the Related Art
In recent years, accompanying the increase in the market of portable terminals equipped with the imaging device, small-sized solid-state image pickup elements with a high number of pixels are mounted to the imaging devices. Corresponding to the downsizing and increase in the number of pixels of the imaging element, the image pickup lens is required to have higher performance in view of resolution and image quality, and with wide use thereof, the image pickup lens is also requested to reduce cost.
In order to satisfy such trend for improving performance, the image pickup lens configured from a plurality of lenses is becoming popular. And, in comparison with the lens configuration of two to three lenses, the image pickup lens of a four-lens configuration which is capable of improving performance than in the lens configuration of two to three lenses is also being proposed.
For example, in Japanese Patent Application Laid-Open No. 2007-286153 (Patent document 1), Japanese Patent Application Laid-Open No. 2008-046526 (Patent document 2), and Japanese Patent Application Laid-Open No. 2008-242180 (Patent document 3), there are disclosed an image pickup lens including, in order from an object side, an aperture stop, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a negative refractive power with at least one surface thereof being an aspheric surface, aiming at improving performance.
Further, in Japanese Patent Application Laid-Open No. 2009-14899 (Patent document 4), there is disclosed an image pickup lens including, in order from the object side, an aperture stop, a first lens having a positive refractive power with a biconvex shape, a second lens of a meniscus shape having a negative refractive power with a convex surface facing the object side, a third lens of a meniscus shape having a positive refractive power with a convex surface facing an image side, and a fourth lens of a meniscus shape having a negative refractive power with a convex surface facing the object side, aiming at improving performance.
Although the image pickup lenses disclosed in the Patent documents 1 to 4 aim at improving performance by taking the four-lens configuration, it is not sufficient for downsizing and slimming, or correction of various aberrations.